1. Field of the Invention
The present invention relates to a golf ball, and more particularly, to a golf ball which improves the symmetry of the dimple arrangement of the golf ball so that the golf ball may fly a long distance.
2. Description of the Related Art
Various methods for arranging dimples on the surface of a golf ball are proposed to improve the flying performance of the golf ball. When the golf ball is hit by a golf club, it normally rotates clockwise (backspin) about a certain rotation axis. It is not preferable that the dimples are so arranged as to cause the golf ball to have a strong directionality, i.e., it is not preferable that the configuration of the trajectory of the golf ball is varied depending on rotation axes, namely, by the position at which the golf ball is hit by the golf club. This is caused by the unsymmetrical dimple arrangement of the golf ball.
The symmetry of the dimple arrangement of the golf ball differs a little from that in geometry. This means that divided parts of the spherical surface of the golf ball in which dimples are arranged are congruent with each other. Accordingly, a favorable symmetry means that dimples can be arranged in divided parts which are congruent with each other.
In order to improve the symmetry of the dimple arrangement, heretofore, dimple arrangements are basically performed by dividing the spherical surface of the golf ball into spherical parts corresponding to the face of a regular polyhedron (hereinafter referred to as regular icosahedral arrangement). For example, the following dimple arrangements are proposed.
(a) U.S. Pat. No. 4,560,168
The dimple arrangement is based on a regular icosahedron arrangement. According to the disclosure, the spherical surface of a golf ball is divided into 20 congruent parts in which the dimple arrangement is symmetrical.
(b) U.S. Pat. No. 4,720,111
The dimple arrangement is based on a regular octahedral arrangement. According to the disclosure, the spherical surface of a golf ball is divided into eight congruent parts in which the dimple arrangement is symmetrical.
(c) U.S. Pat. No. 4,142,727
The dimple arrangement is based on a regular dodecahedral arrangement. According to the disclosure, the spherical surface of a golf ball is divided into 12 congruent parts in which the dimple arrangement is symmetrical.
(d) G.B. No. 377,354
The dimple arrangement is based on a right polyhedrons arrangement, including arrangement of up to a regular icosahedron.
(e) G.B. No. 1,407,730
The dimple arrangement is based on a right icosahedron arrangement including 252 pieces of dimple.
It is difficult to allow dimple arrangements to be symmetrical in many divided parts in consideration of a parting line formed when the golf ball is manufactured by a pair of hemispherical molds. Further, dimples are adjusted not to fall on the parting line. Therefore, in the known regular polyhedral arrangement art, a regular icosahedral arrangement is adopted to divide the spherical surface of the golf ball, but the spherical surface thereof cannot be divided more than 20 parts.